[George83728]

> intense social pressure [...] annoyed looks

That's just... not intense social pressure. That's the least intense social pressure I can imagine.

Refusing to tip a waitress will very likely subject you to intense social pressure; your own friends and family will likely berate you for it on the spot. They'll tell you that you're an asshole and may refuse to eat with you in the future if you establish a pattern of refusing to tip waitresses. The waitress might even dox you on social media for it, and in the past before social media, they might chase you into the parking lot to loudly tell you that you're an asshole taking food from their children's mouths. The manager might chase you down to ask if something was wrong with the service, or tell you that you aren't welcome back.

Refusing to leave money in a tip jar is nothing like that, nobody says a thing. The most you'll ever get is a surly look from the person behind the counter and in all likelihood their poor attitude that day had nothing to do with you. They do work in retail after all, they have a hundred other reasons to be in a bad mood that have nothing to do with you. Follow the golden rule and be courteous to them, but don't let them walk all over you. If they glare at you, just take it in stride; they don't have American culture or customs on their side. Waitresses do.